AUGUSTA – Prosecutors on Wednesday identified a 14-year-old murder suspect as a boy who lived in the same neighborhood as the teenage victim, but refused to say what may have led to the weekend slaying.

Patrick Armstrong of Fayette is charged with killing Marlee Johnston, also 14, on Saturday, the Attorney General’s Office said.

Armstrong was being detained in a juvenile facility pending a hearing in District Court in Augusta on Thursday morning, Deputy Attorney General William Stokes said. What led to the killing remained a mystery Wednesday.

Stokes would not release any details about the investigation, what caused Johnston’s death or the suspect’s background. No decision has been made on whether the state will seek to try Armstrong as a juvenile or an adult.

“Because of the nature of the case, we are not saying whether he was a classmate” of the victim, said Stokes.

Johnston was an eighth-grader at Winthrop Middle School, but an official with the superintendent’s office said Armstrong was not a student at the school. Armstrong lived in the same neighborhood in the rural town since he was a baby.

Homicide investigators are barred by law from releasing the suspect’s identity, state police Lt. Gary Wright said. But a petition filed with the District Court lists Armstrong’s name, address and charge against him. His family lives a street over from the Johnston family’s home.

No additional arrests were expected in connection with Johnston’s death, Wright said.

The killing of Johnston left residents of the quiet central Maine town of about 1,000 in shock. Fayette is 18 miles west of Augusta.

“Not knowing, and not having any information, just exacerbated our anxiety about what has happened,” Town Manager Mark Robinson told WCSH-TV. “However, knowing it is one of our own is another ordeal all on its own, and compassion needs to be shown for the family of the young man who committed this heinous crime.”

Armstrong’s attorney, Walter McKee, said his client should not be subjected to an adult trial because he is so young. A murder conviction in adult proceedings can bring a sentence of 25 years to life in Maine.

Johnston had finished watching a movie with her older brother and was walking the family’s two dogs when she failed to return home Saturday. Her 17-year-old brother, Alec, and father, Ted Johnston, went looking for the girl along a small road and dirt pathways near nearby Lovejoy Pond. Alec Johnston found his sister’s body in the pond.

Before Tuesday’s arrest, authorities advised residents of the area to take precautions such as locking their doors and having a companion when walking in isolated areas. Police patrols in the town were increased.

The last homicide in Fayette was 22 years ago. The stabbing death of Judith Flagg in her home remains unsolved.

A memorial service for Johnston has been scheduled for Thursday afternoon at the private Kents Hill School.